Gurgaon investors: How do you calculate true all-in cost?

Hidden charges in Gurgaon properties are a real headache for investors, honestly. I'm upgrading from my 2BHK in Sector 51 to a 3BHK. Pre-launch deals from Bestech seem tempting, but OC, PLC, maintenance security – it all adds up later. Does that pre-launch discount just become an illusion? What's your trick for the *true* all-in cost?